The EE agency receptionist is just that, they are generally not the managing pimp who advertises girls over a number of websites, so the price a punter pays includes two cuts as well as the girl's cash.
I use agencies regularly and having built up a level of understanding, nearly said trust but remembered what industry this is, 80% of the time, get what I want in terms of looks, attitude and service, a much better hit rate for me than AW, so it's worth paying a premium.